The present disclosure relates to a system and method for measuring the level of fluid in a container and more specifically to measuring the level of fluid in a container based on an electrochemical reaction between measuring probes.
Electrical probes for measuring the level of fluid in a container are known in the art. Such probes are located either on the inside or outside of a container and are used to measure the resistance or capacitance of materials within the container to determine the level of fluid in the container. This disclosure focuses on the use of such containers with recreational vehicles (RVs), however it will be understood that the systems disclosed herein could be used for measuring any container with fluid.
Resistance-based probes for fluid-level measurements are used often in RVs to monitor the level of fluid in the many containers used for storing supplies and waste. Many of these probe systems are subject to inaccurate measurements over time due to residues that accumulate on container interiors between the probes and/or on the surface of the probes. This accumulation often results in an abnormal electrical resistance path between the probes, as compared to a container without interior surface residue accumulation.
In most RVs, wastewater from sinks and showers is stored in one or more “gray water” containers, waste from toilets is stored in one or more “black water” containers, and fresh water supply is held in one or more separate “fresh water” containers. Most RVs include a rather simple system for measuring how full those containers are. Most commonly, the containers are monitored by electrical resistance-based probes and a resistance-based monitoring system. Those systems typically include three measuring probes and a ground probe. The three measuring probes are typically arranged in vertically spaced relation of equal distances along the inner surface of one side of a container, for denoting when the container is empty, ⅓ full, ⅔ full, or entirely full. The container is made of a non-conductive material and the probes are most often made of a stainless steel. The probes penetrate the container to provide an electrical connection through the container wall.
After a number of container empty/fill cycles, the resistance-based monitoring systems provide less accurate and less reliable measurements of black and gray water container levels compared to the freshwater container level. Those inaccurate results are most commonly due to an accumulation of sludge, soap scum, or other materials on the inside of the container walls and/or on the probe surfaces. Sludge build-up provides a low electrical resistance path between the probes and causes electrical resistance-based monitors to inaccurately determine that a probe is submerged in water even when it is not.
Inaccurate container measurements cause frustration and anxiety for many RV owners. They can cause an RV owner to interrupt his or her vacation to drive to the dump station and empty the supposedly full gray and/or black water containers. When the owner reaches the dump station, he or she realizes that the containers may actually be empty or only partially full, either of which do not require a trip to the dump station. Some RV owners spend considerable time and money rinsing and cleaning their containers just to keep the container sensors working reasonably well. In addition to the time that is wasted, frequently cleaning a container to ensure the monitor system works properly requires additional resources which costs more money and can harm the environment.
In addition to the resistance-based monitoring systems typically found in RVs, capacitance-based systems can also be used, typically as a retrofit system. The capacitance-based monitoring systems currently available in the market utilize capacitance probes that are not in contact with the material inside the container but instead use conductive plates affixed to the outside surface of the containers, creating a standard capacitance-based system with dielectric material between plate.
These capacitance-based monitoring systems typically require their special capacitance probes to be applied to the container surfaces at various levels, rather than using standard and/or existing probes, and thus are more expensive for the RV manufacturers to purchase and install compared to the very simple resistance-based probes. Some owners of RVs that come with resistance-based probe monitoring systems purchase and install one of the capacitance-based monitoring systems to obtain more accurate and reliable container level monitoring, but the installation can be difficult and costly.